[tab-under] Enable on fieldtrial_testing_configs

In preparation for a beta experiment.

Bug: 661629
Change-Id: Ie63bdcbfb9e610bdfa0aa925b3f9e21644baacb8
Reviewed-on: https://chromium-review.googlesource.com/922002
Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Commit-Queue: Charlie Harrison <csharrison@chromium.org>
Cr-Commit-Position: refs/heads/master@{#537115}
2 files changed